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The Earth Sciences Portal

Earth seen from Moon

Earth science orgeoscience includes all fields ofnatural science related to the planetEarth. This is a branch of science dealing with the physical, chemical, and biological complex constitutions and synergistic linkages of Earth's four spheres: thebiosphere,hydrosphere/cryosphere,atmosphere, andgeosphere (orlithosphere). Earth science can be considered to be a branch ofplanetary science but with a much older history. (Full article...)

Selected articles

$Image 1 The ACFEL ice auger showing an ice core pushed up into the core remover barrel Ice drilling allows scientists studying glaciers and ice sheets to gain access to what is beneath the ice, to take measurements along the interior of the ice, and to retrieve samples. Instruments can be placed in the drilled holes to record temperature, pressure, speed, direction of movement, and for other scientific research, such as neutrino detection. Many different methods have been used since 1840, when the first scientific ice drilling expedition attempted to drill through the Unteraargletscher in the Alps. Two early methods were percussion, in which the ice is fractured and pulverized, and rotary drilling, a method often used in mineral exploration for rock drilling. In the 1940s, thermal drills began to be used; these drills melt the ice by heating the drill. Drills that use jets of hot water or steam to bore through ice soon followed. A growing interest in ice cores, used for palaeoclimatological research, led to ice coring drills being developed in the 1950s and 1960s, and there are now many different coring drills in use. For obtaining ice cores from deep holes, most investigators use cable-suspended electromechanical drills, which use an armoured cable to carry electrical power to a mechanical drill at the bottom of the borehole. (Full article...)$
Image 1
The ACFEL ice auger showing an ice core pushed up into the core remover barrel

Ice drilling allows scientists studyingglaciers andice sheets to gain access to what is beneath the ice, to take measurements along the interior of the ice, and to retrieve samples. Instruments can be placed in the drilled holes to record temperature, pressure, speed, direction of movement, and for other scientific research, such asneutrino detection.

Many different methods have been used since 1840, when the first scientific ice drilling expedition attempted to drill through theUnteraargletscher in theAlps. Two early methods were percussion, in which the ice is fractured and pulverized, and rotary drilling, a method often used in mineral exploration for rock drilling. In the 1940s, thermal drills began to be used; these drills melt the ice by heating the drill. Drills that use jets of hot water or steam to bore through ice soon followed. A growing interest inice cores, used forpalaeoclimatological research, led to ice coring drills being developed in the 1950s and 1960s, and there are now many different coring drills in use. For obtaining ice cores from deep holes, most investigators use cable-suspended electromechanical drills, which use an armoured cable to carry electrical power to a mechanical drill at the bottom of the borehole. (Full article...)
Image 2

A map of Earth as it appeared 60 million years ago during the Paleocene Epoch, Selandian Age

ThePaleocene (IPA:/ˈpæli.əsiːn,-i.oʊ-,ˈpeɪli-/PAL-ee-ə-seen, -⁠ee-oh-,PAY-lee-), orPalaeocene, is a geologicalepoch that lasted from about 66 to 56Ma (million years ago). It is the first epoch of thePaleogene Period in the modernCenozoic Era. The name comes fromAncient Greek παλαιός (palaiós), meaning "old", andκαινός (kainós), meaning "new", translating to "the old part of the Eocene".

The epoch is bracketed by two major events in Earth's history. TheK–Pg extinction event, brought on by an asteroid impact (Chicxulub impact) and possibly volcanism (Deccan Traps), marked the beginning of the Paleocene and killed off 75% of species, most famously the non-avian dinosaurs. The end of the epoch was marked by thePaleocene–Eocene Thermal Maximum (PETM), which was a major climatic event wherein about 2,500–4,500 gigatons of carbon were released into the atmosphere and ocean systems, causing a spike in global temperatures andocean acidification. (Full article...)
Image 3

Imaging fromNASA's Shuttle Radar Topography MissionSTS-99 reveals part of the diameter ring of the crater in the form of a shallow circular trough. Numerouscenotes (sinkholes) cluster around the trough marking the inner crater rim.

TheChicxulub crater is animpact crater buried underneath theYucatán Peninsula in Mexico. Its center is offshore, but the crater is named after the onshore community ofChicxulub Pueblo (not the larger coastal town ofChicxulub Puerto). It was formed slightly over 66million years ago when anasteroid, about ten kilometers (six miles) in diameter, struckEarth. The crater is estimated to be 200 kilometers (120 miles) in diameter and 30 kilometers (19 miles) in depth. It is one of thelargest impact structures on Earth, alongside the much olderSudbury andVredefort impact structures, and the only one whosepeak ring is intact and directly accessible for scientific research.

The crater was discovered by Antonio Camargo andGlen Penfield, geophysicists who had been looking for petroleum in the Yucatán Peninsula during the late 1970s. Penfield was initially unable to obtain evidence that the geological feature was a crater and gave up his search. Later, through contact withAlan R. Hildebrand in 1990, Penfield obtained samples that suggested it was an impact feature. Evidence for the crater's impact origin includesshocked quartz, agravity anomaly, andtektites in surrounding areas. (Full article...)
Image 4

The BerlinArchaeopteryx specimen (A. siemensii)

Archaeopteryx (/ˌɑːrkiːˈɒptərɪks/ ^ⓘ;lit. 'ancient wing'), sometimes referred to by its German name, "Urvogel" (lit.Primeval Bird) is a genus ofbird-likedinosaurs. Thegenus name derives from theAncient Greekἀρχαῖος (archaîos), meaning "ancient", andπτέρυξ (ptérux), meaning "feather, wing". Between the late 19th century and the early 21st century,Archaeopteryx was generally accepted bypalaeontologists and popular reference books as the oldest known bird (member of the groupAvialae). Older potentialavialans have since been identified, includingAnchiornis,Xiaotingia,Aurornis, andBaminornis.

Archaeopteryx lived in theLate Jurassic around 150 million years ago, in what is now southern Germany, during a time when Europe was anarchipelago of islands in a shallow warm tropical sea, much closer to theequator than it is now. Similar in size to aEurasian magpie, with the largest individuals possibly attaining the size of araven, the largest species ofArchaeopteryx could grow to about 50 cm (20 in) in length. Despite their small size, broad wings, and inferred ability to fly or glide,Archaeopteryx had more in common with other smallMesozoic dinosaurs than with modern birds. In particular, they shared the following features with thedromaeosaurids andtroodontids: jaws with sharpteeth, three fingers withclaws, a long bony tail, hyperextensible second toes ("killing claw"), feathers (which also suggestwarm-bloodedness), and various features of theskeleton. (Full article...)
Image 5

Gloria near peak intensity north ofHispaniola on September 24

Hurricane Gloria was a powerfultropical cyclone that caused significant damage along theEast Coast of the United States and inAtlantic Canada during the1985 Atlantic hurricane season. It was the first significant tropical cyclone to strike the northeastern United States sinceHurricane Agnes in1972 and the first major storm to affect New York City andLong Island directly sinceHurricane Donna in1960. Gloria was aCape Verde hurricane originating from atropical wave on September 16 in the eastern Atlantic Ocean. After remaining a weak tropical cyclone for several days, Gloria intensified into a hurricane on September 22 north of theLesser Antilles. During that time, the storm had moved generally westward, although it turned to the northwest due to a weakening of theridge. Gloria quickly intensified on September 24, and the next day reached peak winds of 145 mph (233 km/h). The hurricane weakened before striking theOuter Banks of North Carolina on September 27. Later that day, Gloria made two subsequent landfalls onLong Island and across the coastline of westernConnecticut, before becomingextratropical on September 28 over New England. The remnants moved through Atlantic Canada and went on to impact Western Europe, eventually dissipating on October 4.

Before Gloria made landfall, theNational Hurricane Center issuedhurricane warnings at some point for theEast Coast of the United States from South Carolina to Maine. Hundreds of thousands of people evacuated, and the hurricane was described as the "storm of the century." In general, Gloria's strongest winds remained east of the center, which largely spared locations from North Carolina to New Jersey, and the passage at low tide reducedstorm surge. Hurricane-force winds and gusts affected much of the path, which knocked down trees and power lines. This left over 4 million people without power, causing the worst power outage in Connecticut history related to anatural disaster. Fallen trees caused six of the storm's fourteen deaths. (Full article...)
Image 6

Grand Canyon of the Yellowstone

Yellowstone National Park is anational park of the United States located in the northwest corner of thestate ofWyoming, with small portions extending intoMontana andIdaho. It was established by the42nd U.S. Congress through theYellowstone National Park Protection Act and signed into law by PresidentUlysses S. Grant on March 1, 1872. Yellowstone was the first national park in the US, and is also widely understood to be the first national park in the world. The park is known forits wildlife andits many geothermal features, especially theOld Faithful geyser, one of its most popular. While it represents many types ofbiomes,subalpine forest is the most abundant. It is part of theSouth Central Rockies forests ecoregion.

While Native Americans have lived in the Yellowstone region for at least 11,000 years, aside from visits bymountain men during the early-to-mid-19th century, organized exploration did not begin until the late 1860s. Management and control of the park originally fell under the jurisdiction of theU.S. Department of the Interior, the firstsecretary of the interior to supervise the park beingColumbus Delano. However, the U.S. Army was eventually commissioned to oversee the management of Yellowstone for 30 years between 1886 and 1916. In 1917, the administration of the park was transferred to theNational Park Service, which had been created the previous year. Hundreds of structures have been built and are protected for their architectural andhistorical significance, and researchers have examined more than one thousand indigenousarchaeological sites. (Full article...)
Image 7

Cannikin warhead being lowered into test shaft

Amchitka Island (/æmˈtʃɪtkə/;Aleut:Amchixtax̂;^{[page needed]}) is a volcanic,tectonically unstable and uninhabited
island in theRat Islands group of theAleutian Islands in southwestAlaska. It is part of theAlaska Maritime National Wildlife Refuge. The island, with a land area of roughly 116 square miles (300 km²), is about 42 miles (68 km) long and 1 to 4 miles (1.6 to 6.4 km) wide. The area has amaritime climate, with many storms, and mostly overcast skies.

Amchitka was populated for more than 2,500 years by theAleut people, but has had no permanent population since 1832. The island has been part of the United States since theAlaska Purchase of 1867. DuringWorld War II, it was used as an airfield by US forces in theAleutian Islands Campaign. (Full article...)
Image 8

Yosemite Valley fromTunnel View

Yosemite National Park (/joʊˈsɛmɪti/yoh-SEM-ih-tee) is anational park of the United States inCalifornia. It is bordered on the southeast by theSierra National Forest and on the northwest byStanislaus National Forest. The park is managed by theNational Park Service and covers 1,187 sq mi (3,070 km²) in fourcounties – centered inTuolumne andMariposa, extending north and east toMono and south toMadera. Designated aWorld Heritage Site in 1984, Yosemite is internationally recognized for its granite cliffs, waterfalls, clear streams, groves ofgiant sequoia, lakes, mountains, meadows, glaciers, andbiological diversity. Almost 95 percent of the park is designatedwilderness. Yosemite is one of the largest and least fragmented habitat blocks in theSierra Nevada mountain range.

Itsgeology is characterized bygranite and remnants of older rock. About 10 million years ago, the Sierra Nevada wasuplifted and tilted to form its unique slopes, which increased the steepness of stream and river beds, forming deep, narrow canyons. About one million years ago,glaciers formed at higher elevations. They moved downslope, cutting and sculpting the U-shapedYosemite Valley. (Full article...)
Image 9
Old Faithful erupting atYellowstone National Park

Ageyser (/ˈɡaɪzər/,UK:/ˈɡiːzər/) is aspring with an intermittent water discharge ejected turbulently and accompanied by steam. The formation of geysers is fairly rare and is caused by particularhydrogeological conditions that exist only in a few places on Earth.

Generally, geyser field sites are located near activevolcanic areas, and the geyser effect is due to the proximity ofmagma. Surface water works its way down to an average depth of around 2,000 metres (6,600 ft) where it contacts hot rocks. The pressurized water boils, and this causes the geyser effect of hot water and steam spraying out of the geyser's surface vent. (Full article...)
Image 10
Geologic time shown in a diagram called a geological clock, showing the relative lengths of the eons of Earth's history and noting major events

Thegeological history of Earth follows the major geological events in Earth's past based on thegeologic time scale, a system ofchronological measurement based on the study of the planet's rock layers (stratigraphy). Earth formedapproximately 4.54 billion years ago through accretion from thesolar nebula, a disk-shaped mass of dust and gas remaining from the formation of the Sun, which also formed the rest of theSolar System.

Initially, Earth was molten due to extremevolcanism and frequent collisions with other bodies. Eventually, the outer layer of the planet cooled to form a solidcrust when water began accumulating in the atmosphere. TheMoon formed soon afterwards, possibly as a result of the impact of aprotoplanet with Earth.Outgassing and volcanic activity produced the primordial atmosphere.Condensing water vapor, augmented by ice delivered fromasteroids,produced the oceans. However, in 2020, researchers reported thatsufficient water to fill the oceans may have always been onEarth since the beginning of the planet's formation. (Full article...)
Image 11

View of Mount Samalas along with Mount Rinjani

In 1257, a catastrophic eruption occurred at Samalas, avolcano on the Indonesian island ofLombok. The event had a probableVolcanic Explosivity Index of 7, making it one of the largest volcanic eruptions during theHolocene epoch. It left behind a largecaldera that containsLake Segara Anak. Later volcanic activity created more volcanic centres in the caldera, including the Barujari cone, which remains active.

The event createderuption columns reaching tens of kilometres into the atmosphere andpyroclastic flows that buried much of Lombok and crossed the sea to reach the neighbouring island ofSumbawa. The flows destroyed human habitations, including the city ofPamatan, which was the capital of a kingdom on Lombok. Ash from the eruption fell as far as 340 kilometres (210 mi) away inJava; the volcano deposited more than 10 cubic kilometres (2.4 cu mi) of rocks and ash. (Full article...)
Image 12

Darwin,c. 1854, when he was preparingOn the Origin of Species

Charles Robert Darwin (/ˈdɑːrwɪn/DAR-win; 12 February 1809 – 19 April 1882) was an Englishnaturalist,geologist, andbiologist, widely known for his contributions toevolutionary biology. His proposition that allspecies of life have descended from acommon ancestor is now generally accepted and considered a fundamental scientific concept. In a joint presentation withAlfred Russel Wallace, he introduced his scientific theory that thisbranching pattern ofevolution resulted from a process he callednatural selection, in which thestruggle for existence has a similar effect to the artificial selection involved inselective breeding. Darwin has been described as one of the most influential figures inhuman history and was honoured byburial in Westminster Abbey.

Darwin's early interest in nature led him to neglect his medical education at theUniversity of Edinburgh; instead, he helpedGrant to investigatemarine invertebrates. His studies at theUniversity of Cambridge'sChrist's College from 1828 to 1831 encouraged his passion fornatural science. However, it was hisfive-year voyage onHMS Beagle from 1831 to 1836 that truly established Darwin as an eminent geologist. The observations and theories he developed during his voyage supportedCharles Lyell'sconcept of gradual geological change. Publication of hisjournal of the voyage made Darwin famous as a popular author. His first scientific work wasThe Structure and Distribution of Coral Reefs (1842). Along with his work onbarnacles, it won him theRoyal Medal in 1853. (Full article...)
Image 13

Changes insurface air temperature over the past 50 years. TheArctic has warmed the most, and temperatures on land have generally increased more thansea surface temperatures.

Present-dayclimate change includes bothglobal warming—the ongoing increase inglobal average temperature—and its wider effects on Earth'sclimate system.Climate change in a broader sense also includes previous long-term changes to Earth'sclimate. The current rise in global temperatures isdriven by human activities, especiallyfossil fuel (coal,oil andnatural gas) burning since theIndustrial Revolution. Fossil fuel use,deforestation, and someagricultural and industrial practices releasegreenhouse gases. These gasesabsorb some of the heat that the Earthradiates after it warms from sunlight, warming the lower atmosphere.Carbon dioxide, the primary gas driving global warming,has increased in concentration by about 50% since thepre-industrial era to levels not seen for millions of years.

Climate change has an increasingly largeimpact on the environment.Deserts are expanding, whileheat waves andwildfires are becoming more common.Amplified warming in the Arctic has contributed to thawingpermafrost,retreat of glaciers andsea ice decline. Higher temperatures are also causingmore intense storms,droughts, and otherweather extremes. Rapid environmental change inmountains,coral reefs, andthe Arctic is forcing many species to relocate orbecome extinct. Even if efforts to minimize future warming are successful, some effects will continue for centuries. These includeocean heating,ocean acidification andsea level rise. (Full article...)
Image 14
Ice core sample taken from drill

Anice core is acore sample that is typically removed from anice sheet or a high mountainglacier. Since the ice forms from the incremental buildup of annual layers of snow, lower layers are older than upper ones, and an ice core contains ice formed over a range of years. Cores aredrilled with handaugers (for shallow holes) or powered drills; they can reach depths of over two miles (3.2 km), and contain ice up to 800,000 years old.

The physical properties of the ice and of material trapped in it can be used to reconstruct the climate over the age range of the core. The proportions of different oxygen and hydrogenisotopes provide information aboutancient temperatures, and theair trapped in tiny bubbles can be analysed to determine the level of atmospheric gases such ascarbon dioxide. Sinceheat flow in a large ice sheet is very slow, the borehole temperature is another indicator of temperature in the past. This data can be combined to find theclimate model that best fits all the available data. (Full article...)
Image 15

A map of Earth as it appeared during the mid-Ediacaran,c. 600 Ma

TheEdiacaran (/ˌiːdiˈækərən,ˌɛdi-/EE-dee-AK-ər-ən,ED-ee-) is ageological period of theNeoproterozoic Era that spans 96 million years from the end of theCryogenian Period at 635Mya to the beginning of theCambrian Period at 538.8 Mya.^[1] It is the last period of theProterozoic Eon as well as the last of the so-called "Precambrian supereon", before the beginning of the subsequent Cambrian Period marks the start of thePhanerozoic Eon, where recognizablefossil evidence oflife becomes common.

The Ediacaran Period is named after theEdiacara Hills ofSouth Australia, wheretrace fossils of a diverse community of previously unrecognized lifeforms (later named theEdiacaran biota) were first discovered by geologistReg Sprigg in 1946. Its status as an official geological period was ratified in 2004 by theInternational Union of Geological Sciences (IUGS), making it the first new geological period declared in 120 years. Although the period tooknamesake from the Ediacara Hills in theNilpena Ediacara National Park, thetype section is actually located in the bed of theEnorama Creek within the Brachina Gorge in theIkara-Flinders Ranges National Park, at , approximately 55 km (34 mi) southeast of the Ediacara Hills fossil site. (Full article...)
Image 16
Thetornado outbreak of April 6–8, 2006, was a majortornado outbreak in thecentral and parts of the southern United States that began on April 6, 2006, in theGreat Plains and continued until April 8 inSouth Carolina, with most of the activity on April 7. The hardest-hit region wasMiddle Tennessee, where several strong tornadoes devastated entire neighborhoods and left ten people dead. Some of the worst damage took place inGallatin, Tennessee, and other communities north ofNashville also sustained significant damage.

There were 73 tornadoes confirmed across 13 states, with the bulk of them coming on the afternoon and evening of April 7 across the South, particularly inTennessee. In total, 10 deaths were reported as a result of the tornadoes, and over $650 million in damage was reported, of which over $630 million was in Middle Tennessee. It was the third major outbreak of 2006, occurring just days afteranother major outbreak on April 2. It was also considered by some to be the worst disaster event in Middle Tennessee since the1998 tornado outbreak. (Full article...)
Image 17

The2002 Bou'in-Zahra earthquake (also known as the2002 Avaj earthquake or the2002 Changureh earthquake) occurred on 22 June 2002. Theepicenter was near the city ofBou'in-Zahra inQazvin province, a region of northwesternIran which is crossed by several majorfaults that is known for destructive earthquakes. The shock measured 6.5 on theM_wc scale, had a maximumMercalli intensity of VIII (Severe), and was followed by more than 20aftershocks. At least 261 people were killed and 1,500 more were injured.

According to the International Institute of Earthquake Engineering and Seismology (IIEES), the earthquake was felt as far away as the capital city ofTehran, approximately 290 kilometres (180 mi) east of the epicenter, although no damage was reported there. Most houses in the region were single-storymasonry buildings, and virtually all of these collapsed. The public became angry due to the slow official response to victims who needed supplies. Residents of the town ofAvaj resorted to throwing stones at the car of a government minister. (Full article...)
Image 18

Turquoise is anopaque,blue-to-green mineral that is ahydrous phosphate ofcopper andaluminium, with thechemical formulaCu Al₆(PO₄)₄(OH)₈·4H₂O. It is rare and valuable in finer grades and has been prized as agemstone for millennia due to its hue.

Therobin egg blue orsky blue color of thePersian turquoise mined near the modern city ofNishapur,Iran, has been used as a guiding reference for evaluating turquoise quality. (Full article...)
Image 19

Panoramic winter view of Crater Lake fromRim Village

Crater Lake (Klamath:Giiwas) is avolcanic crater lake in south-centralOregon in theWestern United States. It is the main feature ofCrater Lake National Park and is a tourist attraction for its deep blue color andwater clarity. The lake partly fills a 2,148-foot-deep (655 m)caldera that was formed around 7,700 (± 150) years ago
by the collapse of the volcanoMount Mazama. No rivers flow into or out of the lake; the evaporation is compensated for by rain and snowfall at a rate such that the total amount of water is replaced every 150 years. With a depth of 1,949 feet (594 m), the lake is thedeepest in the United States. In the world, it ranks eleventh for maximum depth, as well as fifth for mean depth.

Crater Lake features two small islands.Wizard Island, located near the western shore of the lake, is acinder cone about 316 acres (128 hectares) in size.Phantom Ship, a natural rock pillar, is located near the southern shore. (Full article...)
Image 20
Alaska'sMcCarty Glacier retreated about 15 kilometres (9.3 mi) in less than a century, and dense, diverse vegetation has become established on the slopes.

Theretreat of glaciers since 1850 is a well-documentedeffect of climate change. The retreat ofmountain glaciers provides evidence for therise in global temperatures since the late 19th century. Examples include mountain glaciers in western North America, Asia,the Alps in central Europe, andtropical andsubtropical regions of South America and Africa. Since glacial mass is affected by long-term climatic changes, e.g.precipitation,mean temperature, andcloud cover, glacial mass changes are one of the most sensitive indicators ofclimate change. The retreat of glaciers is also a major reason forsea level rise. Excluding peripheral glaciers ofice sheets, the total cumulated global glacial losses over the 26 years from 1993 to 2018 were likely 5500 gigatons, or 210 gigatons per year.

On Earth, 99% of glacial ice is contained within vastice sheets (also known as "continental glaciers") in thepolar regions. Glaciers also exist inmountain ranges on every continent other than the Australian mainland, including Oceania's high-latitudeoceanic island countries such asNew Zealand. Glacial bodies larger than 50,000 km² (19,000 sq mi) are calledice sheets. They are several kilometers deep and obscure the underlying topography. (Full article...)
Image 21
Calabozos is aHolocene caldera in centralChile'sMaule Region (7th Region). Part of the ChileanAndes' volcanic segment, it is considered a member of theSouthern Volcanic Zone (SVZ), one of the three distinct volcanic belts of South America. This most active section of the Andes runs along central Chile's western edge, and includes more than 70 of Chile'sstratovolcanoes and volcanic fields. Calabozos lies in an extremely remote area of poorly glaciated mountains.

Calabozos and the majority of the Andean volcanoes formed from thesubduction of the oceanicNazca Plate under the continentalSouth American continental lithosphere. The caldera is in a transitional region between thick and thinlithosphere, and is probably supplied by a pool ofandesitic andrhyolitic magma. It sits on a historic bed of volcanic andplutonic sedimentary rock (rock formed within the Earth) that in turn sits on top of a layer of merged sedimentary andmetamorphic rock. (Full article...)
Image 22
Radiocarbon dating helped verify the authenticity of theDead Sea Scrolls.

Radiocarbon dating (also referred to ascarbon dating orcarbon-14 dating) is a method fordetermining the age of an object containingorganic material by using the properties ofradiocarbon, aradioactive isotope of carbon.

The method was developed in the late 1940s at theUniversity of Chicago byWillard Libby. It is based on the fact that radiocarbon (¹⁴
C) is constantly being created in theEarth's atmosphere by the interaction ofcosmic rays with atmosphericnitrogen. The resulting¹⁴
C combines with atmosphericoxygen to form radioactivecarbon dioxide, which is incorporated into plants byphotosynthesis; animals then acquire¹⁴
C by eating the plants. When the animal or plant dies, it stops exchanging carbon with its environment, and thereafter the amount of¹⁴
C it contains begins to decrease as the¹⁴
C undergoesradioactive decay. Measuring the amount of¹⁴
C in a sample from a dead plant or animal, such as a piece of wood or a fragment of bone, provides information that can be used to calculate when the animal or plant died. The older a sample is, the less¹⁴
C there is to be detected. Thehalf-life of¹⁴
C (the period of time after which half of a given sample will have decayed) is about 5,730 years, so the oldest dates that can be reliably measured by this process date to approximately 50,000 years ago, although special preparation methods occasionally make an accurate analysis of older samples possible. Libby received theNobel Prize in Chemistry for his work in 1960. (Full article...)
Image 23

TheCretaceous–Paleogene (K–Pg)extinction event, formerly known as theCretaceous-Tertiary (K–T)extinction event, was a majormass extinction of three-quarters of the plant and animalspecies on Earth approximately 66 million years ago. The event caused the extinction of all non-aviandinosaurs. Most othertetrapods weighing more than 25 kg (55 lb) also became extinct, with the exception of someectothermic species such assea turtles andcrocodilians. It marked the end of theCretaceous period, and with it theMesozoic era, while heralding the beginning of the current geological era, theCenozoic Era. In thegeologic record, the K–Pg event is marked by a thin layer ofsediment called theK–Pg boundary or K–T boundary, which can be found throughout the world in marine and terrestrial rocks. The boundary clay shows unusually high levels of the metaliridium, which is more common inasteroids than in theEarth's crust.

As originally proposed in 1980 by a team of scientists led byLuis Alvarez and his sonWalter, it is now generally thought that the K–Pg extinction resulted from the impact of amassive asteroid 10 to 15 km (6 to 9 mi) wide, 66 million years ago, causing theChicxulub impact crater and devastating the global environment, mainly through a lingeringimpact winter which haltedphotosynthesis inplants andplankton. The impact hypothesis, also known as theAlvarez hypothesis, was bolstered by the discovery of the 180 km (112 mi) Chicxulub crater in theGulf of Mexico'sYucatán Peninsula in the early 1990s. The temporal match between the ejecta layer, and the onset of the extinctions and the agreement of ecological patterns in the fossil record with modeled environmental perturbations (for example, darkness and cooling), lead to the conclusion that the Chicxulub impact triggered the mass extinction. A 2016 drilling project into the Chicxulubpeak ring confirmed that the peak ring comprisedgranite ejected within minutes from deep in the Earth, but contained hardly anygypsum, the usual sulfate-containing sea floor rock in the region: the gypsum would have vaporized and dispersed as anaerosol into the atmosphere, causing longer-term effects on the climate andfood chain. In October 2019, researchers proposed the mechanisms of the mass extinction, arguing that the Chicxulub asteroid impact event rapidlyacidified the oceans and produced long-lasting effects on the climate. (Full article...)
Image 24
A scene inUttarakhand'sValley of Flowers National Park. In contrast to the rain shadow region of Tirunelveli, the park receives ampleorographic precipitation due to its location in a mountainouswindward-facing region wedged between theZanskars and theGreater Himalayas.

Theclimate of India includes a wide range of weather conditions, influenced by its vast geographic scale and varied topography. Based on theKöppen system,India encompasses a diverse array of climatic subtypes. These range from arid and semi-arid regions in the west to highland, sub-arctic, tundra, and ice cap climates in the northernHimalayan regions, varying with elevation.

TheIndo-Gangetic Plains in thenorth experience ahumid subtropical climate which become moretemperate at higher altitudes, like theSivalik Hills, orcontinental in some areas likeGulmarg. In contrast, much of the south and the east exhibittropical climate conditions, which support lush rainforests in parts of these territories. Many regions have starkly differentmicroclimates, making it one of the most climatically diverse countries in the world. The country's meteorological department follows four seasons with some local adjustments: winter (December to February), summer (March to May), monsoon or south-west monsoon (June to September) and post-monsoon or north-east monsoon (October to November). Some parts of the country with subtropical, temperate or continental climates also experience spring and autumn. (Full article...)
Image 25

Isabel at peak intensity, northeast of theLeeward Islands, on September 11

Hurricane Isabel was a large and powerfulCategory 5 Atlantic hurricane that struck theeast coast of the United States in September 2003. The ninthnamed storm, fifth hurricane, and second major hurricane of theseason, Isabelformed in the easternAtlantic Ocean on September 6 from atropical wave. It moved northwestward through an area with light wind shear and warm waters, resulting in strengthening. Isabel reached peak winds of 165 mph (266 km/h) on September 11. After fluctuating in intensity for four days, Isabel gradually weakened and made landfall on theOuter Banks ofNorth Carolina, with winds of 105 mph (169 km/h) on September 18, or a Category 2 on theSaffir-Simpson scale. Isabel quickly weakened over land and becameextratropical over westernPennsylvania on the next day. On September 20, the extratropical remnants of Isabel were absorbed into another system overEastern Canada.

In North Carolina, the storm surge from Isabel washed out a portion ofHatteras Island to form what was unofficially known asIsabel Inlet. Damage was greatest along the Outer Banks, where thousands of homes were damaged or even destroyed. The worst of the effects of Isabel occurred inVirginia, especially in theHampton Roads area and along the shores of rivers as far west and north asRichmond andBaltimore. Virginia reported the most deaths and damage from the hurricane. About 64% of the damage and 69% of the deaths occurred in North Carolina and Virginia. Electric service was disrupted in areas of Virginia for several days, some more rural areas were without electricity for weeks, and local flooding caused thousands of dollars in damage. (Full article...)

Did you know(auto-generated)

... that thegeology of the Ellsworth Mountains was explored by geologists using motor toboggans in 1961?
... thatKenshi Yonezu's song "Dune" describes his perception of a "desert-like atmosphere" on the video-sharing websiteNiconico?
... that theIowa Colored Cowboys played softball for audiences of over a thousand people, in an atmosphere similar to aHarlem Globetrotters show?
... that the Taiwanese restaurant chainFormosa Chang drew inspiration from McDonald's for its non-greasy atmosphere and corporate practices?
... that English amateur geologistCharlotte Eyton wrote a number of papers and pamphlets on the geology ofthe Wrekin, a part of Shropshire, between 1862 and 1870?
... thatFrederick Murray Trotter had a distinguished career as a field geologist despite losing a part of his skull and an eye to shrapnel during World War I?
... that theApollo 12Solar Wind Spectrometer detected a gas-ionshockwave produced by the impact of the Apollo 13S-IVB stage on thelunar surface?
... that geologistE. Dale Jackson conducted experiments withJello to test theories on the formation of the Hawaiian islands?

More did you know? -show different entries

... that a world map byGerardus Mercator attributes theEarth's magnetic field to amagnetic mountain(pictured) above the Arctic Circle?
... that a team ofarchaeologists discovered afossilizedHan Solo in the rocks ofChina?
... thatforest rings had gone unnoticed by geologists untilaerial photography became a common surveying tool in the 1950s?
... that two researchers have argued that somecobbles should be called "very small boulders"?
... thatswarms of dykes have intruded into Uruguay?
... thatprecarious rock formations were evaluated to estimate thepeak ground acceleration of the1952 Kern County earthquake?

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Image 1Concretions, byMbz1 (fromWikipedia:Featured pictures/Sciences/Geology)
Image 2Cassiterite, byAlchemist-hp (fromWikipedia:Featured pictures/Sciences/Geology)
Image 3Mount Hood reflected inMirror Lake,Oregon. (Credit: Oregon's Mt. Hood Territory.) (fromPortal:Earth sciences/Selected pictures)
Image 4Pyrite, byJJ Harrison (fromWikipedia:Featured pictures/Sciences/Geology)
Image 5TheRichat Structure is adepression in the country ofMauritania, almost 50 km (30 mi) across. It was originally thought to be the impact of ameteorite. Now it is thought to be a symmetricaluplift (circularanticline or dome) that has been exposed toerosion. In thisfalse-color photo,bedrock is brown, sand is yellow and white, vegetation is green, and saltysediments are blue. (Credit:Landsat 7.) (fromPortal:Earth sciences/Selected pictures)
Image 6Diatomaceous earth, byRichard Wheeler (fromWikipedia:Featured pictures/Sciences/Geology)
Image 7Opal, byJJ Harrison (fromWikipedia:Featured pictures/Sciences/Geology)
Image 8A 2002 eruption ofMount Etna, avolcano on theItalian island ofSicily, viewed from theInternational Space Station. (Credit: NASA, with image edits byUser:Darkone.) (fromPortal:Earth sciences/Selected pictures)
Image 9Desert rose, byDidier Descouens (fromWikipedia:Featured pictures/Sciences/Geology)
Image 10Sarychev Peak atExplosive eruption, byNASA (fromWikipedia:Featured pictures/Sciences/Geology)
Image 11Gypsum, byJJ Harrison (fromWikipedia:Featured pictures/Sciences/Geology)
Image 12An October 2002 eruption ofMount Etna, avolcano on theItalian island ofSicily, as seen from theInternational Space Station. Etna is the largest of Italy'sthree active volcanoes and one of the most active in the whole entire world. This eruption, one of Etna's most vigorous in years, was triggered by a series ofearthquakes.Ashfall was reported as far away asLibya, 600 km (373 mi) to the south. (Credit:Expedition 5 crew.) (fromPortal:Earth sciences/Selected pictures)
Image 13Wulfenite, byIifar (fromWikipedia:Featured pictures/Sciences/Geology)
Image 14Vanadinite, byIifar (fromWikipedia:Featured pictures/Sciences/Geology)
Image 15Volcanictephra, byGodot13 (fromWikipedia:Featured pictures/Sciences/Geology)
Image 16Hemimorphite, byIifar (fromWikipedia:Featured pictures/Sciences/Geology)
Image 17Platinum, byAlchemist-hp (fromWikipedia:Featured pictures/Sciences/Geology)
Image 18Antarctica, thecontinent surrounding theEarth'sSouth Pole, is thecoldest place on earth and is almost entirely covered byice. Antarctica was discovered in late January1820. Too cold and dry to support virtually any vascular plants, Antarctica's flora presently consists of around 250lichens, 100mosses, 25-30liverworts, and around 700 terrestrial and aquaticalgal species. (Credit:NASA.) (fromPortal:Earth sciences/Selected pictures)
Image 19Celestine, byIifar (fromWikipedia:Featured pictures/Sciences/Geology)
Image 20Aegirine, byIifar (fromWikipedia:Featured pictures/Sciences/Geology)
Image 21Amethyst, byJJ Harrison (fromWikipedia:Featured pictures/Sciences/Geology)
Image 22Hurricane Katrina was the third most powerful storm of the2005 Atlantic hurricane season. It first madelandfall as a Category 1hurricane just north ofMiami, Florida on August 25, 2005, then again onAugust 29 along the Central Gulf Coast nearBuras-Triumph, Louisiana as a Category 4 storm. This photograph of the eye of the hurricane was taken from aNOAA Hurricane Hunter aircraft on August 28, 2005. (Credit:NOAA.) (fromPortal:Earth sciences/Selected pictures)
Image 23Blairmorite, by Paul Glombick (edited byBammesk) (fromWikipedia:Featured pictures/Sciences/Geology)
Image 24Mount Redoubt eruption, by R. Clucas (USGS) (edited byJanke) (fromWikipedia:Featured pictures/Sciences/Geology)
Image 25Satellite image ofCyclone Gafilo, a powerfulCategory 5 tropical cyclone which struckMadagascar in March 2004, causing devastating damage. This was taken just before landfall, when the system was at its peak intensity about 333 km (207 mi) east of Madagascar, with sustained windspeed of 260 km/h (160 mph). At least 250 people were listed dead, with more missing, and 300,000 people were left homeless due to Gafilo. (Credit:Terra satellite,NASA.) (fromPortal:Earth sciences/Selected pictures)
Image 26Pressure release ofgranite in theEnchanted Rock State Natural Area ofTexas,United States. The photo shows the geological exfoliation of granite dome rock. (Taken byWing-Chi Poon on 2nd April 2005.) (fromPortal:Earth sciences/Selected pictures)
Image 27Aragonite, byJJ Harrison (fromWikipedia:Featured pictures/Sciences/Geology)
Image 28Mohawkite, byAlchemist-hp (fromWikipedia:Featured pictures/Sciences/Geology)
Image 29This map shows the tracks of alltropical cyclones that formed worldwide from 1985 to 2005. The points show the locations of the storms at six-hourly intervals and use the color scheme shown on the right from theSaffir-Simpson Hurricane Scale. (Credit:Nilfanion.) (fromPortal:Earth sciences/Selected pictures)
Image 30Thin section scan, byKallerna (fromWikipedia:Featured pictures/Sciences/Geology)
Image 31Glacier retreat is a type ofglacial motion in which more materialablates from its terminus of theglacier than is replenished by flow into that region. In this region of theBhutan-Himalaya, glacial lakes have been rapidly forming on the surface of thedebris-covered glaciers and researchers have found a strongcorrelation betweenincreasing temperatures and glacial retreat. (Credit:NASA &USGS.) (fromPortal:Earth sciences/Selected pictures)
Image 32Crocoite, byJJ Harrison (fromWikipedia:Featured pictures/Sciences/Geology)
Image 33Crystallinedolomite and magnesite, byDidier Descouens (fromWikipedia:Featured pictures/Sciences/Geology)
Image 34Sulfur, byIifar (fromWikipedia:Featured pictures/Sciences/Geology)
Image 35Oceans cover almost three quarters (71%) of the surface of theEarth, and nearly half of the world's marine waters are over 3000 m deep. This global, interconnected body ofsalt water, called the World Ocean, is divided by thecontinents andarchipelagos into the following five bodies, from the largest to the smallest: thePacific Ocean, theAtlantic Ocean, theIndian Ocean, theSouthern Ocean, and theArctic Ocean. Official boundaries are defined by theInternational Hydrographic Organization. (Credit:Alexandre Van de Sande.) (fromPortal:Earth sciences/Selected pictures)
Image 36Incandescent Pahoeoe Fountain atShield volcano, by J.D. Griggs,USGS (fromWikipedia:Featured pictures/Sciences/Geology)
Image 37Weathered rocks atJoshua Tree National Park, byMila Zinkova (fromWikipedia:Featured pictures/Sciences/Geology)
Image 38Dundasite byJJ Harrison (fromWikipedia:Featured pictures/Sciences/Geology)
Image 39Wulfenite, byDidier Descouens (fromWikipedia:Featured pictures/Sciences/Geology)
Image 40Cinnabar, byJJ Harrison (fromWikipedia:Featured pictures/Sciences/Geology)
Image 41Athunderstorm is a form ofsevere weather involvinglightning andthunder. Thunderstorms have had a lasting and powerful influence on mankind. Romans thought them to be battles waged byJupiter. Thunderstorms were associated with theThunderbird, held byNative Americans to be a servant of theGreat Spirit. (Credit: John Kerstholt.) (fromPortal:Earth sciences/Selected pictures)
Image 42The world's largestcompass rose, drawn on the desert floor atEdwards Air Force Base inCalifornia,United States. Painted on theplaya nearDryden Flight Research Center, it is inclined tomagnetic north and is used by pilots for calibratingheading indicators. (Credit:NASA.) (fromPortal:Earth sciences/Selected pictures)
Image 43Malachite, byJJ Harrison (fromWikipedia:Featured pictures/Sciences/Geology)
Image 44Sand particles, bySiim (fromWikipedia:Featured pictures/Sciences/Geology)
Image 45Pyromorphite, byIifar (fromWikipedia:Featured pictures/Sciences/Geology)
Image 46A true-color picture ofIreland, as seen from space, with theAtlantic Ocean to the west and theIrish Sea to the east. (fromPortal:Earth sciences/Selected pictures)
Image 47Winter is one of the fourseasons of temperate zones.Meteorological winter is the season having the shortest days (which vary greatly according tolatitude) and the lowest temperatures. (Credit:Richard Fabi.) (fromPortal:Earth sciences/Selected pictures)
Image 48Baryte, byIifar (fromWikipedia:Featured pictures/Sciences/Geology)
Image 49Atacamite, byIifar (fromWikipedia:Featured pictures/Sciences/Geology)
Image 50Bultfonteinite, byIifar (fromWikipedia:Featured pictures/Sciences/Geology)
Image 51Specimen from a palaeontological site of Lebanon atPaleontology in Lebanon, byMila Zinkova (fromWikipedia:Featured pictures/Sciences/Geology)
Image 52Azurite, byIifar (fromWikipedia:Featured pictures/Sciences/Geology)
Image 53Smoky quartz, byJJ Harrison (fromWikipedia:Featured pictures/Sciences/Geology)
Image 54Sandstone, byMoondigger (fromWikipedia:Featured pictures/Sciences/Geology)
Image 55Rhodochrosite, byJJ Harrison (fromWikipedia:Featured pictures/Sciences/Geology)
Image 56Cirrus clouds are composed ofice crystals and shaped like hairlike filaments. They are formed at an altitudes above 5000 metres (16,500 feet). The streaks are made ofsnowflakes that are falling from the cloud and being caught by the high level winds. The streaks point in the direction of the wind and may appear straight giving the clouds the appearance of a comma (cirrus uncinus), or may by seem tangled, an indication of high levelturbulence. (Credit:Piccolo Namek.) (fromPortal:Earth sciences/Selected pictures)
Image 57Erosion of the bluff in Pacifica, bymbz1 (fromWikipedia:Featured pictures/Sciences/Geology)
Image 58Petrified wood, byDaniel Schwen (fromWikipedia:Featured pictures/Sciences/Geology)
Image 59Tsunami in Thailand at2004 Indian Ocean earthquake and tsunami, by David Rydevik (fromWikipedia:Featured pictures/Sciences/Geology)
Image 60Prehnite, byIifar (fromWikipedia:Featured pictures/Sciences/Geology)
Image 61Astronauts aboard the Space Shuttle Discovery recorded this rarely seen phenomenon of the fullMoon partially obscured by theatmosphere of Earth. The image was recorded with an electronic still camera at 15:15:15 GMT, Dec. 21, 1999. (Credit:NASA.) (fromPortal:Earth sciences/Selected pictures)
Image 62Ant trapped in Balticamber, byBaltic-amber-beetle (edited byAmericanXplorer13) (fromWikipedia:Featured pictures/Sciences/Geology)
Image 63Stellerite, byIifar (fromWikipedia:Featured pictures/Sciences/Geology)
Image 64Creedite, byJJ Harrison (fromWikipedia:Featured pictures/Sciences/Geology)
Image 65Petrified log atPetrified Forest National Park, byMoondigger (fromWikipedia:Featured pictures/Sciences/Geology)
Image 66Azurite, byJJ Harrison (fromWikipedia:Featured pictures/Sciences/Geology)
Image 67Northern shoremeadows ofSihlsee, anartificial lake nearEinsiedeln in theCanton of Schwyz,Switzerland. (Credit:Markus Bernet.) (fromPortal:Earth sciences/Selected pictures)
Image 68Quartz, byJJ Harrison (fromWikipedia:Featured pictures/Sciences/Geology)
Image 69Erg Chebbi (Arabic:عرج شبّي) is the soleSaharan erg inMorocco. It is 22 km long (North-South) and 5 km wide. Its dunes reach a maximum height of 150 meters. It is located roughly 40 kilometers south-east ofErfoud. The local center for tourists is the village ofMerzouga. (Credit:Rosa Cabecinhas and Alcino Cunha.) (fromPortal:Earth sciences/Selected pictures)
Image 70Acanthite, byIifar (fromWikipedia:Featured pictures/Sciences/Geology)
Image 712004 Indian Ocean Earthquake tsunami at2004 Indian Ocean earthquake and tsunami, by Vasily V. Titov,NOAA (edited byVeledan) (fromWikipedia:Featured pictures/Sciences/Geology)
Image 72Cerussite, byIifar (fromWikipedia:Featured pictures/Sciences/Geology)
Image 73Mimetite, byIifar (fromWikipedia:Featured pictures/Sciences/Geology)
Image 74Himalayan salt, byIifar (fromWikipedia:Featured pictures/Sciences/Geology)
Image 75Atmospheric gases scatter blue wavelengths of visible light more than other wavelengths, giving the Earth’s visible edge a blue halo. At higher and higher altitudes, the atmosphere becomes so thin that it essentially ceases to exist. Gradually, the atmospheric halo fades into the blackness of space. (Credit:NASA's Earth Observatory.) (fromPortal:Earth sciences/Selected pictures)

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21 November 2025 –2025 Bangladesh earthquake: A M_w 5.5earthquake strikes centralBangladesh, killing ten people and wounding over 350 more.(AA)(Jamuna Television)
3 November 2025 –2025 Balkh earthquake: A M_w 6.3 earthquake strikes nearMazar-i-Sharif,Balkh,Afghanistan, killing at least 20 people, injuring hundreds others, and damaging the historicBlue Mosque.(Reuters)(DW)

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